How far apart should I space my spindles? How many do I need?

This is usually the starting point for those looking to buy spindles or balusters for their porch.  The following is a baluster spacing guide for meeting the 4″ ball rule required by most building codes.  Of course if codes don’t apply in your situation, you can space them farther for an airy/sparse look, or closer for more robust feel.

1 5/8″ Wood Spindle / Turned Baluster

Spacing & Quantity: To meet the 4″ ball rule required by most building codes, space these spindles every 4 3/4″ On Center.  The smallest diameter of the turned portion is approx. 7/8″, so with a 4 3/4″ O.C. spacing, you’ll have a 3 7/8″ gap between them at the narrowest portion.

2 1/2″ Wood or Polyurethane Spindle / Turned Baluster

Spacing & Quantity: To meet the 4″ ball rule required by most building codes, space these spindles every 5 1/4″ On Center.  The smallest diameter of the turned portion is approx. 1 3/8″, so with a 5 1/4″ O.C. spacing, you’ll have a 3 7/8″ gap between them at the narrowest portion.  To determine quantity required, take your rail length in inches and divide by 5.25.

3 1/2″ Wood or Polyurethane Spindle / Turned Baluster

Spacing & Quantity: To meet the 4″ ball rule required by most building codes, space these spindles according to the following On Center spacing:
Revival: 5 1/2″ O.C.
Victorian: 5 3/4″ O.C.
Tuscan: 5 3/4″ O.C.
Colonial: 5 7/8″ O.C.
Classic: 6″ O.C.
Using the above spacing, you’ll have a 3 7/8″ gap between spindles at the narrowest portion.

4 1/2″ Polyurethane Spindle / Turned Baluster

Spacing & Quantity: To meet the 4″ ball rule required by most building codes, space these spindles every 6 1/4″ On Center.  To determine quantity required, take your rail length in inches and divide by 6.25.

5 1/4″ Polyurethane Spindle / Turned Baluster

Spacing & Quantity: To meet the 4″ ball rule required by most building codes, space these spindles every 6 7/8″ On Center.  To determine quantity required, take your rail length in inches and divide by 6.875.

7 1/2″ Polyurethane Spindle / Turned Baluster

Spacing & Quantity: To meet the 4″ ball rule required by most building codes, space these spindles every 7 3/4″ On Center.  To determine quantity required, take your rail length in inches and divide by 7.75.

Square Balusters, Wood or Composite

For square baluster spacing, simply add 3 7/8″ to the width, and that should be your on-center spacing.  It will leave a 3 7/8″ gap between them:
1 5/8″ wide Wood Baluster: 5 1/2″ on-center
1 3/4″ wide Polyurethane Baluster: 5 5/8″ on-center
2 1/4″ wide Polyurethane Baluster: 6 1/8″ on-center
2 1/2″ wide Wood Baluster: 6 3/8″ on-center
3 1/2″ wide Wood Baluster: 7 3/8″ on-center

So how many spindles or balusters do I need for my porch railing?

To come up with the quantity, take the length of rail (in inches) and divide by the on-center spacing, and subtract one.  You subtract one because they will be centered in the rail between two posts, columns, etc.  For example, you have a 8′ rail (96 inches) and are using the 3 1/2″ Classic Porch Spindle (our best seller).  96 divided by 6 = 16.  Minus 1 = 15.  So you’ll need 15 spindles for an 8′ section of rail.

UPDATE: There are many “apps” that can be downloaded to your smartphone to make this job very easy.  Just search “baluster spacing app” or something similar, and you should have several options (both paid and free).  These apps will help you keep the exact same spacing between all spindles/balusters regardless of the length of rail section.

 

2 thoughts on “How far apart should I space my spindles? How many do I need?”

  1. we are going to have a new railing with 3 inch glass spindles (balusters?) installed. What kind of space should there be between those kind of spindles?
    Thanks so much for you help!!!

    1. Thanks for the question. I’m not sure the exact design of your spindles, but with our 2 1/2″ Turned Porch Spindles, you’ll want to space them every 5″ on center. With the 2 1/2″ Square Balusters, a 6″ on-center spacing will work well. If you send us a picture or diagram of your spindles, we can recommend a spacing.

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